Electron beam pantograph control



July 9, 1968 Filed Aug. 6, 1964 MHHUH EEUU'EVE J. A. HANSEN ETAL3,392,262

ELECTRON BEAM PANTOGRAPH CONTROL 3 Sheets-Sheet 1 l/a/m/z ##7761 L 0\on. w Avraar/gy July 9, 1968 J. A. HANSEN ETAL ELECTRON BEAM PANTOGRAPHCONTROL Filed Aug. 6, 1964 5 Sheets-Sheet 2 yr wm" y 1968 J. A. HANSENETAL 3,

ELECTRON BEAM PANTOGRAPH CONTROL Filed Aug. 6, 1964 3 Sheets-Sheet 5 Z/f f7- United States Patent 3,392,262 ELECTRON BEAM PANTOGRAPH CONTROLJohn A. Hansen, Granby, and John E. Mattox, Wapping, Conn., assignors toUnited Aircraft Corporation, East Hartford, Conn., a corporation ofDelaware Filed Aug. 6, 1964, Ser. No. 387,927 6 Claims. (Cl. 219121)ABSTRACT OF THE DISCLOSURE Apparatus for serially positioning :aplurality of objects to be electron beam welded in line with an electronbeam generator and moving each object under the beam in accordance witha pattern, the pattern being in the form of a movable template, motionof a template tracer for the movable template being transmitted into theevacuated work chamber of the electron beam generator and coupled to anobject supporting table via a pantograph having linkages interior andexterior of the evacuated chamber, motion of the template itself causingthe supporting table to be engaged at a new location.

This invention relates to the automatic control of tools. Moreparticularly, this invention is directed to a device which effectscontrol over an operation which is to be performed in a locationinaccessible to the operator of the tool.

While not limited thereto, this invention is thought to have particularutility and thus will be described in connection with the control of thepositioning of a workpiece which is to be operated upon within theevacuated work chamber of an electron beam machine. Electron beammachines, as they are now generally known, are devices which use thekinetic energy of an electron beam to work a material. US. Patent No.2,987,610, issued June 6, 1961, to K. H. Steigerwald, discloses such amachine. These machines operate by generating a beam of electrons havingextremely high beam power density. An electron beam is a welding,cutting and machining tool which has practically no mass but has highkinetic energy because of the extremely high velocity imparted to theelectrons. Transfer of this kinetic energy to the lattice electrons ofthe workpiece generates higher lattice vibrations which cause anincrease in the temperature Within the impingement area sufiicint toaccomplish work. As taught by the above-mentioned Steigerwald patent,once a minimum or threshold value for beam power density has beenexceeded, the beam of electrons will penetrate deeply into the workproducing a narrow, highly heated channel without reliance upon thermalconduction through the workpiece material.

It is, of course, necessary that the beam of electrons be generated in alow pressure environment. This requirement is dictated by, among otherthings, the fact that the elements which emit or otherwise causeproduction of the electrons, which are thereafter focussed into a beam,are highly susceptible to damage. In the usual instance the electronsare emitted by an incandescent, tungsten filament. Any oxygen in thechamber where the filament is located will cause almost instantaneousoxidation and failure of said filament. Once the emitted electrons havebeen focussed, by means clearly shown in the above-mentioned Steigerwaldpatent, into a beam, they will be accelerated and focussed at thedesired point on the surface of the workpiece. Recent advances in thestate of the art have permitted positioning of the workpiece outside ofthe low pressure environment and bringing the beam out of said lowpressure region to perform its work in the atmosphere. While suchout-of-vacuum electron beam material working unquestionably has great3,392,262 Patented July 9, 1968 See utility, particularly in the weldingor machining of large workpieces, there are many instances where it ismore desirable to locate the work in the same low pressure environmentwhere the beam is generated. One particularly significant reason forplacing the workpiece in a vacuum chamber is that, because of scatter ofthe beam due to collisions between the electrons and air molecules,greater power is required to achieve results outside the vacu um whichare comparable with similar work performed in an evacuated chamber.

Many schemes have been proposed for the manipulation of workpiecespositioned in inaccessible locations. These prior art schemesuniversally suffer from the same deficiencies. That is, they arerelatively expensive, complex and, due in part to their complexity, havelong down times when trouble develops. Examples of such prior artschemes are computed programming of Work table position and theprovision of plural manipulators which extend into the inaccessibleregion. 'It is the primary object of this invention to provide for themovement of a workpiece positioned in an inaccessible location by meanswhich are inexpensive, reliable, fast acting and not unduly complex. Inaddition, this invention achieves the foregoing in automated fashion.

It is therefore an object of this invention to provide for the automaticcontrol of a tool.

It is another object of this invention to automatically control thepositioning of a workpiece in an inaccessible location.

It is also an object of this invention to provide for the automaticcontrol of a process to be performed within an evacuated chamber.

It is a further object of this invention to automatically position aworkpiece located within the work chamber of an electron beam machine.

It is yet another object of this invention to transmit motion from theexterior to the interior of a chamber without coincidence leakage of thefluid which comprises the exterior environment through the wall of thechamber.

These and other objects of this invention are achieved by a novelprogramming mechanism which employs a pantograph having an externalparallelogram located outside of a chamber in which work is to beperformed and having its follower linkage located within said chamber. Astylus or template tracer is attached to a first corner of the externalparallelogram and is driven around a template. The motion imparted tothe pantograph linkages is transmitted, by a novel arrangement ofcoaxial shafts, through the wall of the chamber so as to drive thelinkages of the follower parallelogram. The corner of the secondparallelogram engages, by means of a retractable pin, a table carryingone or a plurality of workpieces and thus causes movement of the workbeneath the tool in accordance with the pattern being followed by thestylus. Means are also provided which permit the automatic positioningof a series of workpieces under the tool.

This invention may be better understood and its numerous advantages willbecome apparent to those skilled in the art by reference to theaccompanying drawing wherein like reference numerals refer to likeelements in the different figures and in which:

FIGURE 1 is an isometric drawing of the control which comprises thisinvention.

FIGURE 2 is a plan view of the follower linkage employed in theapparatus shown in FIGURE 1.

FIGURE 3 is a side elevation view of the apparatus shown in FIGURE 2.

FIGURE 4 is a sectional view, along line 4-4 of FIGURE 2, of the meansemployed in the apparatus of 3 FIGURE 1 for transmitting motion throughthe wall of the chamber.

Referring now to FIGURE 1, the programming mechanism which comprisesthis invention is shown being utilized to control the positioning ofworkpieces beneath a stationary electron beam in the evacuated workchamber of an electron beam welding machine. The electron beam machineemploys an electron beam forming column 10, only the bottom of which isshown, which comprises basically the same components as the beam formingcolumn shown in FIGURE 1 of the aforementioned Steigerwald patent. Theelectron beam, which may be focussed to a diameter of .001 inch, exitsfrom beam forming column through tube 12. The beam thereafter impingesupon a workpiece located in work chamber 14 and aligned with the axis ofthe beam. Both chamber 14 and column 10 are evacuated by vacuum pumpingmeans, not shown. In FIGURE 1, the pieces to be worked comprise aplurality of electronic devices which are to be hermeticallyencapsulated by the welding of cans thereover. These devices, with thecans in place, are positioned in a tray 16 carried in a rack 17 which ismovable in the X and Y directions beneath the beam forming column. Tray16 has apertures 19 in the bottom thereof for engagement with a drivepin 18 extending from a drive pin assembly 21 and which, in the mannerto be described below, moves in accordance with a remotely locatedpattern. Rack 17 is slideably mounted on a pair of support rods and 22and thus can move freely in the Y direction. Rods 20 and 22 are fixed tomembers 24 and 26 and together therewith form a carriage which is freelymovable in the X direction by rolling along a pair of rails 28 and 30.When drive pin 18 is withdrawn from tray 16, the entire assembly may bemoved in either the X or Y direction by engagement of a solenoidoperated alternate drive pin 32 carried by a movable table indicatedgenerally at 34 which travels along guides mounted on the bottom of workchamber 14. The movement of mechanism 34 may be programmed but, in themost usual case, will be controlled by a pair of hand wheels, not shown,such as wheels 35 and of FIGURE 1 of the abovementioned Steigerwaldpatent.

In the apparatus shown in FIGURE 1, welding motion is achieved bypositioning each individual workpiece, one at a time, under the beam andthen moving the entire tray through coordinated XY motion such that eachportion to be welded on each device passes under the beam. Thiscoordinated XY motion is programmed by driving a template tracer orstylus 42 around a template. Motion of the template tracer istransmitted, by means of a pantograph linkage, to drive pin 18. As willbe discussed in more detail below, motion of the template tracer isreproduced on a reduced scale at the work tray to provide the XY motion.By adjusting the pantograph linkages, in a manner well known in the art,the demagnification may be selected and the welding contour thusadjusted to the desired value. In one embodiment, Work tray 16 carried140 pieces and the demagnification ratio was variable between 1:4 and1:10.

In order to drive template tracer 42, a tracer drive motor 36 is mountedon a frame 38 above the template 40. Drive motor 36 drives the templatetracer mechanism 42 through a constant velocity, double universal,telescoping shaft 44. Template 40 is mounted on a base 41 and isfabricated by forming a chain as the outside edge. Template tracer 42comprises a sprocket which engages said chain to provide for positivedrive action. The foregoing arrangement provides for constant speedmovement of the stylus 42 about the template and this in turn providesthe requisite constant speed movement of the work under the beam; evenwhen the stylus is rotating about the corners of the template. As shouldbe obvious, constant speed of movement of the work is necessary toproduce uniform welds. For purposes which will be more fully explainedbelow, the template and base assembly are movable in the Y direction,along slides 46 and 48, under the command of air cylinder or actuator50.

The operation of a pantograph is, of course, well known in the art. Inthe apparatus being described, pantograph linkages 52 and 53, whichcomprise the external large parallelogram, move in response to thetracing of template 40 by template tracer 42. Motion of linkages 52 and53 is transmitted through the wall of chamber 14, without coincidentleakage of air into the evacuated chamber, by means, located in ahousing 54, which will be described in more detail below. Inside ofchamber 14, motion of linkages 52 and 53 will cause correspondingmovement of linkages 56 and 57 of the follower parallelogram. In orderto facilitate the transmission of the motion of the pantograph linkage52 to follower linkage 56, chamber 14 is constructed with a V-shapeddepression, indicated generally at 58, in the side thereof. The pivotpoint of the external parallelogram is located adjacent the apex of thisdepression. As will be clearly explained below, movement of linkages 52,53 will be transmitted vertically through to top wall 59 of depression58 to the pivot point of the internal parallelogram.

Referring now to FIGURES 2 and 3, the internal parallelogram is shown intop plan and side elevation views respectively. FIGURE 3 most clearlyshows the means, discussed above, by which the drive pin 18 may beretracted from tray 16 after welding of each individual device. As ismost clearly seen from FIGURE 4, drive pin 18 is spring biased intoengagement with the apertures 19 in the work tray duning a weldingoperation. At the completion of a weld, pin 18 is retracted byenergizing solenoid 60 which is connected to pin 18 by means of aflexible shaft 62. As will be explained in more detail below, pin 18will thereafter move in such a manner as to engage the next aperture inthe Work tray and will move said tray in such a manner that thesucceeding workpiece will be aligned with the axis of the electron beam.The foregoing manner of indexing constitutes a substantial improvementover the prior art because it eliminates accumulated tolerances. Thatis, by so moving the Work in a stepwise fashion rather than programmingthe entire movement of tray 16 from a single starting point, accumulatederrors are eliminated.

Considering now FIGURE 4, the means for transmitting the motion ofpantograph linkages 52 and 53 of the external parallelogram through thewall 59 of depression 58 in vacuum chamber 14 is shown in detail.Pantograph linkage 53 of the external parallelogram is keyed to a firstshaft '70 and is held by means of a locking nut 72. Pantograph linkage52 of the external parallelogram is similarly keyed to a hollow shaft 74and is held in place thereon by locking nut 76. Shaft 74 is coaxial withshaft and, while serving to support the same, is capable of rotatingthereabout on bearings 78 and 80. The assembly comprising coaxial shafts70 and 74 is rigidly mounted to housing 54 which is in turn welded totop wall 59 of depression 58. The inside of housing 54 is constructedwith a shoulder 81 which receives the outer race 82 of bearing 84. Theinner race 83 of bearing 84 is retained on shaft '74 by means of aretaining ring 88. Between the lower bearing 84 and an upper bearing ispositioned a spacer ring 92. Spacer ring 92 supports the outer race 94of bearing 90 and the inner race 96 of this bearing is also retained bya shoulder on shaft 74. The inner race 96 of bearing 90 is retained inposition and thus rotatably supports shaft 74 by means of a locking nut97 which engages threads on shaft 74. The bearings are also retained bymeans of the top 98 of housing 54 which has a projection 99 thereonwhich abuts outer race 94 and thus holds the bearing assembly in theproper position. Top member 98 is held into position on housing 54 bymeans of screws 100. Prior to bolting top 98 on member 54, a vacuum seal102 is positioned on an inner shoulder of member 54. Tightening ofscrews 100 compresses seal 102 and thereby prevents leakage of air fromwithout chamber 14 into the chamber around bearings 84 and 90. Alsopositioned between top member 98 and outer shaft 74 are a pair of vacuumseals 104. Seals 104 circumscribe and squeeze against shaft 74 thuspreventing leakage of air into chamber 14 around the outside of shaft 74while still permitting rotation of the shaft. To prevent leakage of airbetween shafts 70 and 74, another set of vacuum seals 106 is provided.Seals 106, as well as the outer races of bearing 80, are held inposition by a locking nut and seal retainer 108. As with shaft 74, shaft70 can rotate within seals 106. Follower linkage 57 is keyed to theupper end of shaft 74 and thus rotation of shaft 74 will cause movementof pin 18 which is similarly keyed to linkage 57. Linkage 56 is keyed tothe upper end of shaft 70 and thus rotation of shaft 70 will also causemovement of pin 18 to which linkage 56 is also keyed. As mentionedabove, pin 18 will engage the apertures in the work tray through theaction of a spring. For this purpose, a spring 110 is providedinternally of pin assembly 18. Thus, pin 18 will firmly engage the worktray until such time as solenoid 60 is activated whereupon shaft 62 willpull downwardly against the spring tension and cause retraction of pin18. Upon deenergization of solenoid 60, pin 18 will be urged upwards andwill engage an aperture in tray 16. Upon engagement of pin 18 with a pinaperture, a welding operation may be initiated.

Referring again to FIGURE 1, the operation of the disclosed invention isas follows. Assuming drive pin 18 is engaged in an aperture in tray 16,the operator will close a switch, not shown, to initiate welding. Uponclosing of this switch, motor 36 will begin driving templatetracer orstylus assembly 42 about the template 40 in the clockwise direction fromits starting position. The starting position is with the stylus 42 incontact with and thus causing closing of limit switch 112 which ismounted on the template support member 41. When the stylus moves out ofcontact with switch 112, the switch will open and, through the action ofstate-of-the-art electromechanical circuitry contained in a sequencer orlogic unit 114, the electron beam generator will be gated on. Throughthe action of thepantograph, the workpiece Will then be moved beneaththe beam in accordance with the template pattern. The template tracerwill rotate about template 40 one complete time. When stylus 42 contactsand thus closes switch 112 a second time, a timer in logic unit 114 willbe actuated. The timer will prevent the second closing of switch 112from deenergizing the beam generator and motor 36 and thus will producea desired overlapping of the weld seam. The timer therefore functions asa holding relay for a predetermined interval and, when it has counteddown to zero, will permit the deenergization of the beam generator. Atthis time, through relay circuits in unit 114, the motor 36 will beenergized with a reverse polarity signal and will back up until switch112 is contacted. Upon recontacting of switch 112 by stylus assembly 42,solenoid 60 will be energized thereby causing retraction of drive pin18. Also upon reclosing of switch 112, air cylinder or actuator 50 willbe energized and will drive the template and tracer assembly to the leftas shown in FIGURE 1. During this period, switch 112, which travels withthe template assembly, will act as an interlock and will preventenergization of motor 36 and the beam generator. The motion of template40 and tracer 42 will be terminated by the contacting of a second limitswitch 116, mounted on an adjustable stop 117, by the template supportmember 41. Closing of switch 116 deenergizes air actuator 50 therebypermitting the template and tracer assembly to return to its startingposition. Closing of switch 116 also deenergizes solenoid 60 per mittingspring 110 to cause pin 18 to engage a succeeding aperture in the rowbeing worked. Return of the template assembly to its initial positionthus causes a simultaneous movement of the work tray so as to position asecond device to be welded in line with the axis of the beam. Uponreturn to its starting position, an extension on template support 41will contact and thus close switch 118. Closing of switch 118 will breakthe relay circuits held closed by switch 112 and thus will causereenergization of motor 36 and the beam generator. Thereafter the entireprocedure will be repeated until a complete row of devices on tray 16have been worked. When a row has been completed, the machine operatorwill deactivate the sequencer and will engage alternate drive pin 32with work tray 16. The operator will then drive table 34 in such amanner that a second row of devices to be worked is lined up with thebeam axis. The operator will next cause retraction of pin 32, energizethe sequencer and a second row may be automatically worked. It should benoted that the stepping from row to row need not be performed manuallybut can, through relatively straight-forward electromechanical logiccircuitry which is controlled through limit switches on rack 17, beperformed automatically. In moving of table 34 so as to position a newrow on tray 16 in line for working, it is necessary that the tray 16 bemoved in only one direction. By means of an interchange switch, notshown, on sequencer unit 114, the mode of indexing of the tray along arow can be reversed so that automatic operation up and down alternaterows is achieved. The foregoing is accomplished simply by alternatingthe sequence of retraction of drive pin 18 so that, after completing arow operating in the mode described above, the next row is worked withthe drive pin being retracted, under command of switch 116, aftermovement of the template to the left, solenoid 60 being deenergized byclosing of switch 118.

While a preferred embodiment has been shown and described, variousmodifications and substitutions may be made without deviating from thescope and spirit of this invention. For example, with an electron beammachine employing a movable gun assembly, this invention may be employedto control movement of the gun relative to a stationary workpiecewithout the exercise of invention. Similarly, this invention may beutilized to control either the position of a device which generates abeam of coherent light or the objects to be worked with such a beam. Itis to be understood that the invention is not limited to the specificembodiment herein illustrated and described but may be used in otherways without departure from its spirit as defined by the followingclaims.

We claim:

1. Apparatus for automatically controlling the position and motion of aplurality of bodies to be worked with an electron beam within theevacuated work chamber of an electron beam machine comprising:

a template located outside of the evacuated work chamber of the electronbeam machine,

a template tracer,

means for driving said template tracer about said template with constantspeed,

means coupled to said template tracer for converting the linear motionthereof to rotary motion,

means for transmitting said rotary motion through a wall of theevacuated chamber without coincident leakage of air,

a movable table for supporting the bodies to be worked within theevacuated chamber,

means positioned in said evacuated chamber for engaging and driving saidtable,

means positioned in said evacuated chamber and coupled to said tableengaging means and to said rotary motion transmitting means forreconverting said rotary motion to linear motion, means for moving saidtemplate, and

means responsive to the motion of the template for causing said engagingmeans to engage said movable table at a new location whereby saidplurality of bodies may be serially moved into position beneath the beamgenerator and thereafter moved under the beam in accordance with thepattern defined by the template.

2. The apparatus of claim 1 wherein said means for causing engagement ofthe engaging means with the table comprises:

first means responsive to the complete tracing of the template by thetemplate tracer for causing disengagement of the engaging means from thetable,

second means responsive to the complete tracing of the template by thetemplate tracer for generating a control signal for activating saidmeans for simultaneously moving said template and tracer,

means responsive to a desired degree of movement of said template forcausing reengagement of said engaging means with the table at a newlocation, and

means responsive to the return of the template to its starting point forcausing said template tracer to begin retracing said template.

3. The apparatus of claim 2 wherein said means for transmitting rotarymotion through said wall of the chamber comprises:

a pair of coaxial shafts arranged for rotation about each other, theouter of said shafts being rotatably mounted in said wall of thechamber,

first sealing means positioned between said inner and outer shafts,

second sealing means positioned between outer shaft and said wall.

4. Apparatus for automatically controlling the position and motion of aplurality of bodies in an environment unsuitable to the presence of aWorkman comprising:

means located in a friendly environment and carrying a pattern it isdesired to have each of the bodies follow,

a pattern tracer,

means for driving said pattern tracer about said pattern with constantspeed,

means coupled to said pattern tracer for transmitting the motion thereofinto the unsuitable environment Without coincident leakage of fluidbetween said unsuitable and friendly environments,

a movable table for supporting the bodies within the unsuitableenvironment,

means located within said unsuitable environment for engaging anddriving said table,

means connecting said table engaging means to said motion transmittingmeans for coupling said transmitted motion to said table engaging meanswhereby said table and pattern tracer move simultaneously during thedriving of said pattern tracer about said pattern,

means for simultaneously moving said attern carrying and pattern tracingmeans and,

means responsive to said simultaneous motion of the pattern tracing andcarrying means for causing said engaging means to engage said table at anew location.

5. Apparatus for automatically controlling the position and motion of aplurality of bodies to be worked in an environment unsuitable to thepresence of a workman comprising:

a template located in a friendly environment,

a template tracer,

means for driving said template tracer about said template with constantspeed,

a first parallelogram formed by the linkages of a pantograph coupled atone corner to said template tracer,

means connected to the opposite corner of said first parallelogram fortransmitting motion of the template tracer into the unsuitableenvironment without coincident leakage of fluid between said unsuitableand friendly environments,

a movable table for supporting the bodies to be worked within theunsuitable environment,

means for engaging and driving said table,

a second parallelogram of said pantograph positioned within theunsuitable environment and connecting said table driving means to saidmotion transmitting means for coupling said transmitted motion to saidsaid table,

means for moving said template, and

means responsive to motion of the template for causing said engagingmeans to engage said table at a new location.

6. Apparatus for automatically controlling relative motion in anevacuated chamber between an object to be worked with a beam of chargedparticles and the normal axis of the beam comprising:

means located outside of the evacuated chamber and carrying a patternthat it is desired to have the object follow,

a pattern tracer,

means for driving said pattern tracer about said pattern with constantspeed,

means coupler to said pattern tracer for transmitting the linear motionthereof into the evacuated chamher as rotary motion Without coincidentleakage of an,

means within said chamber and operatively connected to said motiontransmitting means for converting the transmitted rotary motion backinto linear motion, and

means in said chamber responsive to said linear motion causing relativemovement between the object to be worked and the axis of the beam ofcharged particles.

References Cited UNITED STATES PATENTS 184,493 11/1876 Anderson 33251,923,208 8/1933 Howey 33-25 1,943,205 1/1934 Coradi 3325 2,261,64411/1941 Cockrell 219- 2,679,620 5/1954 Berry 219124 2,987,610 6/1961Steigerwald 219121 3,037,888 6/1962 Lobosco et a1. 219125 3,049,6088/1962 Greene 219-121 RICHARD M. WOOD, Primary Examiner.

W. D. BROOKS, Assistant Examiner.

